Pump device for high pressure fuel delivery in fuel injection system of internal combustion engines

ABSTRACT

The invention relates to a pump device for high-pressure fuel delivery in fuel injection systems of internal combustion engines, in particular in a common rail injection system, including a radial piston pump (2, 68, 80) with a drive shaft (38, 74, 114) that is supported in a pump housing (14) and is embodied eccentrically or has cam-like projections in the circumference direction, preferably with a number of pistons that are each disposed in a cylinder chamber radially in relation to the drive shaft and can be driven to reciprocate in the cylinder chamber when the drive shaft rotates, and with a check valve on the intake side and the high pressure side, and a low pressure pump (4, 71, 82) connected before the radial piston pump; in order to improve the pump device in such a way that it is more compact and can be produced more cheaply and the danger of the occurrence of leaks is reduced, the low pressure pump (4, 71, 82) is provided on or in the pump housing (14) of the radial piston pump (2, 68, 80), on the end remote from the drive end (10), and can be driven by the drive shaft (38, 74, 114) of the radial piston pump. (FIG. 1b)

PRIOR ART

The invention relates to a pump device for high pressure fuel deliveryin fuel injection systems of internal combustion engines, in particularin a common rail injection system, including a radial piston pump with adrive shaft that is supported in a pump housing and is embodiedeccentrically or has cam-like projections in the circumferencedirection. Preferably a number of pistons are disposed in a cylinderchamber radially in relation to the drive shaft and can be driven toreciprocate in the cylinder chamber when the drive shaft rotates, andincludes a check valve on the intake side and the high pressure side,and a low pressure pump connected before the radial piston pump.

The supply of fuel to the radial piston pump, which produces the highpressure takes place in a known manner by means of a low pressure pumpas the pre-feed pump.

In known pump devices, the low pressure pump is disposed spatiallyseparate from the radial piston pump. The low pressure pump is usuallyembodied as a separate pump and is driven by a shaft of the internalcombustion engine or it is embodied as an electric pump.

In order to accommodate two pumps that are spatially separate from eachother, a corresponding space is required, and additional fasteningpoints must be produced for the pump housing. In addition, it requiresadditional fuel lines in order to connect the low pressure pump to theradial piston pump. As a result, there is an increased danger that leakswill occur.

Based on this, the object of the current invention is to produce a pumpdevice of the type described at the beginning in which theabove-explained disadvantages do not occur. In particular, a compactpump device should be produced that saves space and is inexpensive toproduce.

This object is attained according to the invention by means of a pumpdevice of the type mentioned at the beginning by virtue of the fact thatthe low pressure pump on or in the pump housing of the radial pistonpump is provided on the end remote from the drive end and can be drivenby the drive shaft of the radial piston pump.

This reduces the number and length of the fuel-carrying lines outsidethe pump housing and thus reduces the danger that external leaks willoccur. Furthermore, a very compact construction of the pump device canbe achieved. Because of the savings in housing parts and the realizationof a common drive train, the pump can also be produced more cheaply.

In a preferred manner, a coupling is interposed between the drive shaftof the radial piston pump and a shaft of the low pressure pump. As aresult, assembly or manufacture precision of the components of theradial piston pump and the low pressure pump, in particular flushdeviations of the drive shaft of the radial piston pump and the shaft orof a corresponding shoulder in the low pressure pump can be compensatedfor.

The use of an Oldham coupling has turned out to be suitable,particularly in the embodiment of the low pressure pump as a gear pumpthat is relatively flat in structure.

In a particularly preferred manner, the housing of the low pressure pumpis embodied as essentially disk-shaped, which is why a gear pump hasturned out to be particularly suitable.

The housing of the low pressure pump preferably can be mounted to thepump housing of the radial piston pump by way of a centering means. Tothis end, it turns out to be advantageous if a centering flange thatprotrudes in the direction of the housing of the low pressure pump isprovided on the pump housing of the radial piston pump, with whichflange the housing of the low pressure pump can be positioned. It goeswithout saying that a converse embodiment of the centering flange on thehousing of the low pressure pump is also included in this concept of theinvention.

In order to seal the low pressure pump and the radial piston pump inrelation to the outside, it has turned out to be sufficient andadvantageous to provide an elastomer sealing means that isadvantageously disposed between the centering flange of the radialpiston pump and the housing or an opposing flange or collar of the lowpressure pump.

In order to define the static contact of the two pumps against eachother, it has turned out to be advantageous if the centering flange issupported with its end face against a flat end face of the housing ofthe low pressure pump.

However, it is also possible that the radial piston pump and the lowpressure pump are supported with flat end faces against each other. Insuch an instance, centering means can be embodied, preferably in theform of a number of alignment bores and alignment pins that engage inthem or can also be embodied by threaded bores and alignment screws thatare screwed into them.

The front side of the low pressure pump could lead in an intrinsicallyarbitrary manner to the intake side of the radial piston pump, forexample a relatively short external line section could be provided.However, an embodiment is preferable in which a fuel supply conduitleads away from a pressure chamber of the low pressure pump andcommunicates with a fuel intake opening in the pump housing of theradial piston pump, i.e. the openings in the housing components restingagainst each other feed into one another in a flush manner.

Depending on whether the radial piston pump is fuel-lubricated or islubricated by the lubricating oil circuit of the engine, it turns out tobe advantageous if, in the region of the drive train, an additionalsealing means for preventing leakage from the low pressure pump into thepump housing of the radial piston pump can be dispensed with or isadvantageously provided in order to prevent a leakage of this kind inthe latter instance. If in the latter instance, an additional sealingelement is provided, then it furthermore turns out to be advantageous ifthere is a communication between the shaft region of the low pressurepump and the suction chamber in order to remove the emerging leakageliquid and supply it to the intake side of the radial piston pump.

It should furthermore be mentioned that it turns out to be particularlyadvantageous if the radial piston pump has a solid, monoblock-likecomponent in which bores are provided that constitute the cylinderchambers for the pistons as well as all of the fuel intake openings andhigh pressure-carrying supply openings. The low pressure pump can thenbe attached directly to this component.

Other features, details, and advantages of the invention ensue from thegraphic depiction and subsequent description of preferred embodiments ofthe pump device according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a-1c show three different views of a redial piston pump

FIG. 1d shows a sectional view of a pump device according to theinvention;

FIGS. 1e and f show different views that correspond to FIGS. 1c and 1dwith a different fuel supply;

FIG. 2 is a side view, shown partially cut-away in a longitudinalsection, of a second exemplary embodiment of the pump device accordingto the invention;

FIGS. 3a-3c show three different views of a third embodiment

FIG. 3d shows a sectional view of a pump device according to theinvention in accordance with a third embodiment; and

FIGS. 3e and f show different views that correspond to FIGS. 2c and 2d,3e, f with slight differences.

FIGS. 1a to 1d show a first embodiment of a pump device comprised of aradial piston pump 2, and a low pressure pump 4 in the form of a gearpump 6, which is connected as a pre-feed pump before the radial pistonpump 2. The gear pump 6 is provided with its pump housing 8 on the sideremote from the drive end 10 of the radial piston pump 2 resting againstan end face 12 of a pump housing 14 of the radial piston pump 2. Acentering means 16 in the form of a centering flange 18 protrudes fromthe end face 12 of the pump housing 14 of the radial piston pump 2. Acentering collar 20 of a disk-shaped housing part 22 of the gear pump 6engages in the centering flange 18. Between the contact faces of thecentering flange 18 and the centering collar 20, which are concentric toa drive train 24, an elastomer sealing ring element 26 is provided in anannular groove-shaped recess and seals the gear pump 6 and the radialpiston pump 2 in relation to the outside. The centering flange 18 restswith its axial end face 19 against a flat end face section of thedisk-shaped housing part 22. The gears 28, 30 that mesh with each otherare accommodated disposed non-rotatably on a shaft 32 in the disk-shapedhousing part 22 of the gear pump 6, wherein the shaft 32 is supported sothat it can rotate in the disk-shaped housing part 22. A c losing plate34 is tightened in a sealed fashion against the end face of thedisk-shaped housing part 22 remote from the radial piston pump 2, withthe interposition of an elastomer sealing element 36.

The shaft 32 of the gear pump 6 is disposed flush with a drive shaft 38of the radial piston pump 2 and is drive connected to it by way of anOldham coupling 40, wherein both the drive shaft 38 and the shaft 32 ofthe gear pump 6 are provided with a pin 42 or 44 oriented toward thecoupling.

The supply of fuel to the gear pump 6 takes place by way of a suctionfitting 46 to a suction chamber 48, which is constituted by thedisk-shaped housing part 22. A bore 52 leads away from a pressurechamber 50 of the gear pump 6, travels parallel to the longitudinal axisof the drive train 24, and feeds into the end face 54 of the disk-shapedhousing part 22 that rests against the centering flange 18. The mouth isflush with a fuel supply opening 56 in the pump housing 14 of the radialpiston pump 2, which constitutes the intake side of the radial pistonpump 2. In the sealing face, an elastomer sealing element 58 is providedaround the mouths that are flush with each other.

However, the supply of fuel can also take place from the pump housing(monoblock) by way of a bore 47. The intake fitting 46a is then disposedon the pump housing; this is shown in FIGS. 1e and 1f.

The seal in relation to the outside is produced between the gear pump 6and the radial piston pump 2 by way of the sealing rings 26 and 36. Anadditional seal in the region of the drive train 24 between the gearpump 6 and the radial piston pump 2 is not required since the internallubrication of the radial piston pump 2 takes place by means of thesupplied medium, fuel. It is therefore harmless if a leak can occur inthe region of the drive train 24 from the gear pump 6 into the interiorof the radial piston pump 2.

In contrast to this, in the embodiment according to FIG. 2, thelubrication of the radial piston pump 68 is provided by way of alubricating circuit, not shown, of the internal combustion engine.Therefore, a sealing element 72 is provided concentric to the shaft 70of the low pressure pump 71 and prevents a penetration of fuel from theleakage region that is not to be prevented, around the rotatable driveshaft 70 of the low pressure pump 71 into the region of the drive shaft74 of the radial piston pump 68 that is lubricated by motor oil. Inorder to return the fuel, a communication opening 76 is provided betweena shaft region 78 and the suction chamber of the low pressure pump,which cannot be depicted in FIG. 2.

FIGS. 3a to 3f show another embodiment of a pump device in a verycompact design, wherein the radial piston pump 80 is in turn lubricatedwith fuel. The embodiment to be described below differs from theembodiment according to FIG. 1 by virtue of the fact that the radialpiston pump 80 and the gear pump 82 rest against each other by way offlat contact faces 84 and 86. A closed annular groove is provided in thecontact surface 86 in order to contain an elastomer sealing element 87.A disk-shaped housing part 88 of the gear pump 82 is thus open towardthe contact face 86 of the radial piston pump 80. After the insertion ofthe gears 90, 92, together with the drive shaft 94, a flange plate 96 isplaced against the side of the disk-shaped housing part 88 orientedtoward the contact face 86, with the interposition of an elastomersealing ring 98. The flange plate 96 has through openings 102 that areflush with alignment bores 98, 100, and alignment pins 104 reach throughthese through openings as centering means. Furthermore, alignment screws106 are provided, which reach through screw openings 108 in the flangeplate 96 and are thus screwed into flush threaded bores 110 in thehousing of the radial piston pump 80, by means of which on the one hand,a centering or positioning of the gear pump 82 is achieved and on theother hand, the housing of the gear pump 82 is tightened against thecontact face 86 of the radial piston pump 80. According to FIG. 3e,however, a centering collar 111 can also be provided on the flange plate96a, which engages in the centering flange of the pump housing.Furthermore, the sealing element 87 can also be embodied as a sealingplate 87a (FIG. 3f). The driving of the gear pump 83 is in turn carriedout by the drive shaft 114 of the radial piston pump 80 via a coupling112. The drive shaft 114 is embodied with an internal profile 116 thatis embodied as a six-pointed star. The coupling 112 has acomplementarily embodied opposing profile 118, which produces apositively engaging rotational slaving. On the low pressure pump end,the driven gear 120 is connected to the drive-end coupling part 126 byway of a positively engaging profile 122 that produces a rotationalslaving. Flush deviations between the drive shaft 114 and the gear 120are compensated for by way of the play of the two profile pairings. Theconveyance of the fuel takes place in the same manner as in theembodiment according to FIG. 1, by way of supply openings 128 and 130that are flush with each other. The foregoing relates to preferredexemplary embodiments of the invention, it being understood that othervariants and embodiments thereof are possible within the spirit andscope of the invention, the latter being defined by the appended claims.

What is claimed is:
 1. A pump device for high-pressure fuel delivery infuel injection systems of internal combustion engines, in particular ina common rail injection system, including a radial piston pump (2, 68,80) with a drive shaft (38, 74, 114) that is supported in a pump housing(14) and is embodied eccentrically or has cam-like projections in thecircumference direction, preferably with a number of pistons that areeach disposed in a cylinder chamber radially in relation to the driveshaft and can be driven to reciprocate in the cylinder chamber when thedrive shaft rotates, and with a check valve on the intake side and thehigh pressure side, and a low pressure pump (4, 71, 82) connected beforethe radial piston pump, characterized in that the low pressure pump (4,71, 82) is provided on or in the pump housing (14) of the radial pistonpump (2, 68, 80), on the end remote from the drive end (10), and can bedriven by the drive shaft (38, 74, 114) of the radial piston pump. 2.The pump device according to claim 1, in which a coupling (40, 112) isinterposed between the drive shaft (38, 74, 114) of the radial pistonpump and a shaft (32, 70, 94) of the low pressure pump.
 3. The pumpdevice according to claim 1, in which the housing (8) of the lowpressure pump is mounted to the pump housing (14) of the radial pistonpump by away of a centering means (16).
 4. The pump device according toclaim 2, in which the housing (8) of the low pressure pump is mounted tothe pump housing (14) of the radial piston pump by away of a centeringmeans (16).
 5. The pump device according to claim 3, in which acentering flange (18), which protrudes toward the housing (8) of the lowpressure pump (4), is provided on the pump housing (14) of the radialpiston pump (2) and can be used to position the housing of the lowpressure pump.
 6. The pump device according to claim 4, in which acentering flange (18), which protrudes toward the housing (8) of the lowpressure pump (4), is provided on the pump housing (14) of the radialpiston pump (2) and can be used to position the housing of the lowpressure pump.
 7. The pump device according to claim 5, in which anelastomer sealing means(26) for producing a seal in relation to theoutside is provided between the centering flange (18) of the radialpiston pump (2) and the housing (8) of the low pressure pump (4).
 8. Thepump device according to claim 6, in which an elastomer sealingmeans(26) for producing a seal in relation to the outside is providedbetween the centering flange (18) of the radial piston pump (2) and thehousing (8) of the low pressure pump (4).
 9. The pump device accordingto claim 3, in which the centering flange (18) is supported with its endface (19) against a flat end face of the housing (8) of the low pressurepump.
 10. The pump device according to claim 5, in which the centeringflange (18) is supported with its end face (19) against a flat end faceof the housing (8) of the low pressure pump.
 11. The pump deviceaccording to claim 1, in which the radial piston pump and the highpressure pump rest with flat end faces against each other.
 12. The pumpdevice according to claim 2, in which the radial piston pump and thehigh pressure pump rest with flat end faces against each other.
 13. Thepump device according to claim 3, in which the radial piston pump andthe high pressure pump rest with flat end faces against each other. 14.The pump device according to claim 3, in which the centering means ispreferably constituted by a number of alignment bores (98, 100, 102) andalignment pins (104) that engage in them.
 15. The pump device accordingto claim 7, in which the centering means is preferably constituted by anumber of alignment bores (98, 100, 102) and alignment pins (104) thatengage in them.
 16. The pump device according to claim 9, in which thecentering means is preferably constituted by a number of alignment bores(98, 100, 102) and alignment pins (104) that engage in them.
 17. Thepump device according to claim 11, in which the centering means ispreferably constituted by a number of alignment bores (98, 100, 102) andalignment pins (104) that engage in them.
 18. The pump device accordingto claims 3, in which the centering means is preferably constituted by anumber of threaded bores (110) and alignment screws (106) that arescrewed into them.
 19. The pump device according to claim 1, in which afuel supply conduit (52) leads away from a pressure chamber (50) of thelow pressure pump (4) and communicates with a fuel supply opening (56)in the pump housing (14) of the radial piston pump (2).
 20. The pumpdevice according to claim 1, in which a conduit leads to a suctionchamber (48) of the low pressure pump (4) and communicates with aconduit in the pump housing (14) of the radial piston pump (2) fromwhich the fuel is supplied to the intake side of the low pressure pump(4).
 21. The pump device according to claim 1, in which the radialpiston pump (2, 80) is fuel-lubricated and in the region of the drivetrain (24), no additional sealing means is provided for preventingleakage from the low pressure pump (4) into the pump housing (14) of theradial piston pump (2).
 22. The pump device according to claim 1, inwhich the radial piston pump (68) is lubricated by a lubricating oilcircuit of the engine and that a sealing element (72) is providedconcentric to the drive train in order to prevent leakage from the lowpressure pump (71) into the pump housing of the radial piston pump (68).23. The pump device according to claim 22, in which there is acommunication between the shaft region (78) and the intake chamber ofthe low pressure pump (71) in order to drain away leakage liquid.